1. Field of the Invention
The present invention relates to a zoom lens and an image pick-up apparatus. In particular, the present invention relates to a zoom lens and an image pick-up apparatus using the same, which are suitable for an image pick-up optical system for digital input/output devices, such as a digital still camera, a digital video camera, etc., and which are compact and have a high zooming ratio.
2. Description of Related Art
In recent years, the image pick-up apparatus using a solid-state imaging device, such as a digital still camera etc., has been spreading. As such a digital still camera spreads, there is a need for higher definition. Particularly, in the digital still camera with many pixels etc., there is a need for a lens (especially the zoom lens) for image pick-up excellent in an image forming performance corresponding to the solid-state imaging device with many pixels. Further, there is a strong need for miniaturization, and there is a demand for a small and highly efficient zoom lens. Furthermore, in order to make a camera thinner, some cameras are proposed in which the optical system is bent or folded by inserting a prism between lenses, to attain the thinning (reduction in incidence optical axis direction).
As for such a zoom lens, there is a demand for reduction in overall dimensions as well as the thinning of the lens system in addition to a demand for a higher zooming ratio, as a recent trend.
Examples of a zoom lens in which a prism is inserted between lenses and to attain the thinning are described in Japanese Patent Application Publication (KOKAI) No. 2005-84283, Japanese Patent Application Publication (KOKAI) No. 2005-91465 and Japanese Patent Application Publication (KOKAI) No. 2006-71993.